Packaging material for curing or marinating fresh food during storage has been part of the art for some time. U.S. Pat. No. 6,623,773 for example, issued to Mr. Hans J. Meier, one of the inventors of the instant application, has been granted on Sep. 23, 2003. This document explains the composition of food-seasoning sheet products.
Other known documents describing similar sheet materials include:    U.S. Pat. No. 5,705,214 issued to T. Ito et al., on Jan. 6, 1998;    CA Patent 2,007,522 issued to T. Ito, et al., on Mar. 14, 2000;    US publ. 2009/0274799 published by R. V. Lee et al., on Nov. 5, 2009.
Referring back to the Meier patent, U.S. Pat. No. 6,623,773, which is incorporated herein by reference, it is explained therein that the calibration of seasoning ingredients bonded to a food-seasoning sheet is closely depending on the amount of adhesive that has been applied to the sheet. We might add that the calibration of seasoning ingredients in a food-seasoning sheet is also closely depending on the condition of the adhesive when seasoning ingredients are deposited over the sheet.
Spice products for example, are granular or powdery in nature and their adhesion to a food-seasoning sheet depends on the portion of each granule that sinks into the layer of adhesive. The thickness and surface tension of the adhesive layer are contributing factors in the ability to retain the spice product to a food-seasoning sheet. When the layer of adhesive is too shallow, the surface of the adhesive tends to dry up and to form a shell that does not retain powdery spice materials. A thicker layer of adhesive tends to retain more fluid and wet, and to completely encapsulate and/or dissolve spice particles. In some instances, a thicker layer of adhesive may hinder the release of the spice particles from the sheet and into the food to be marinated. Furthermore, the air and water content of the adhesive are contributing factors to cause more or less absorption of the seasoning ingredients into the adhesive and to modify the potency of these ingredients. Therefore, both the thickness of adhesive and the wetness of this adhesive are important factors to consider in the manufacturing a high quality food-seasoning sheets.
For example, it is well known that HVP's (hydrolyzed vegetable proteins) and sucrose are very moisture-sensitive elements that have the ability to extract moisture from a substrate. This makes these elements very difficult to work with without losing their effectiveness.
The type of adhesive that is used in these applications has a viscous structure. When such an adhesive is discharged from a slot die for example, it may have a foamy texture with air entrapped in it. When air is released from the adhesive, the final volume of adhesive remaining on the sheet is less than the amount calibrated through the slot die. Also, when air is released from the surface of the adhesive, it promotes a faster drying of the surface. Consequently, the wetness of the adhesive applied to a food-seasoning sheet also depends on the air content in the adhesive exiting the slot die. Similarly, the free moisture present in the adhesive tends to dissolve the food-seasoning ingredients into the adhesive and/or into one another and to reduce the potency of the seasoning ingredients.
Because of these factors, basically, it has been difficult in the past to precisely calibrated the amount of adhesive delivered onto a food-seasoning sheet. Therefore, there exists a need for precisely controlling the amount of adhesive that is laid on a food-seasoning sheet and there also exists a need for controlling the amount of air and free moisture present in that adhesive.